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Introduction

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Introduction to the Synthetics Pillar of the Wheat Pre-breeding LoLa / WISP

The Synthetics Pillar is being delivered by NIAB

Overall Aim

The overall aim is to extend the bread wheat gene pool by understanding, exploiting and incorporating novel genetic diversity from diploid and tetraploid Triticeae genomes. The principal objectives are to 1) create backcross lines in adapted germplasm for breeder exploitation using two inter-specific crossing approaches (synthetic hexaploid wheat and hexaploid x tetraploid) 2) develop three wild emmer bi-parental mapping populations as resources for trait dissection and 3) identify founder lines for the future development of chromosome segment substitution lines (CSSL) for QTL mapping and positional cloning.

Background

A large degree of genetic diversity within a very accessible gene pool is available from diploid goat grass (Aegilops tauschii) incorporated in synthetic hexaploid wheat (SHW) and from tetraploid sources such as wild and cultivated emmer wheat (Triticum dicoccoides T. dicoccum) and durum wheat (T. turgidum) used as direct donors in crosses with bread wheat. SHW re-create the original hybridization event that occurred between durum wheat (T. turgidum; 2n=4x=28 AABB) and Ae. tauschii (2n=2x=14 DD) some 10,000 years ago. This approach has been widely used to broaden genetic diversity in bread wheat where there is comparatively little D-genome variation; recent estimates indicate that more than one third of CIMMYT’s advanced breeding lines are SHW derivatives [3].

To demonstrate the UK potential of SHW BBSRC has funded NIAB (BB/E006868/1) to develop backcross lines in adapted wheat genotypes using CIMMYT SHW; in 2009 the NIAB pre-breeding team interrogated an early-generation field nursery in conjunction with commercial breeders. This will be repeated with around 3000 advanced lines in 2010 and a smaller set of interesting lines will be progressed further. In parallel, to extend the use of SHW, the NIAB Trust has supported a 12 month pump-priming project to establish methods for creation of novel SHW, thus allowing exploitation of previously unused D-genomes. To date 24 new SHW have been produced from about 70 crosses. These two areas of expertise now embedded at NIAB will be fully exploited in this new programme.

Objectives

1. Selection of diverse accessions of diploid and tetraploid donor plants (year 1).

2. Production of 50 pentaploid F1 HxTW lines and 50 novel SHW (years 1-2).

3. In Paragon and Robigus produce 2000-2500 BC1F5 lines from 25 cultivated emmer and durum donors and 400-500 BC1F5 lines from pre-project SHW; initiate development of equivalent material from 25 wild emmer and 50 novel synthetic wheat (years1-3).

4. Physiological data on phenotypes expected to affect yield in emmer wheat; select genotypes for mapping population and CSSL production (year 1).

5. Initiate development of 3 wild emmer mapping populations (years 2-3)

6. Single chromosome founder lines from Ae. tauschii and emmer wheat for future production of CSSL populations as resources for QTL mapping and positional cloning (years 2-3)